How are Tachycardia and atrial fibrillation related?

and could you tell me about them. I know that atrial fib. os an abnormal rhythm of the heart, and tachycardia is a fast heart beat but could you tell me more?

tachycardia=means fast heart rate of any source
atrial fibrillation=slow or fast, but abnormal. different pacemakers of the heart firing,, and every now and then an impulse gets through to the ventricles.

Tachycardia is a fast, regular beat. AF is an irregular irregularity.

Supraventricular tachycardia (SVT) is a heart rhythm disorder featuring episodes of abnormally fast heart rate lasting for seconds, minutes, hours or rarely days. Episodes may occur regularly or very infrequently (sometimes years apart).The rate may be as high as 300 beats per minute, but is usually between 140 and 180. It is caused by abnormal, fast, electrical spontaneous impulses that arise in the atria, the upper chambers of the heart and override the natural pacemaker. Attacks often come on for no obvious reason but may be triggered by exertion, emotional upset, coffee or alcohol. In most cases, the heart is normal, although the symptoms may be uncomfortable.
I add a link which discusses this subject.

http://www.nlm.nih.gov/
medlineplus/ency/article
/000187.htm

Atrial fibrillation (AF), the most commonly encountered arrhythmia in clinical practice, is defined by the absence of coordinated atrial systole. AF results from multiple re-entrant electrical wavelets that move randomly around the atria. P waves are replaced by irregular, chaotic fibrillatory waves, often with a concomitant irregular ventricular tachycardia. The rate at which the atrial electrical impulses are transmitted to the ventricle is determined by a number of factors including relative refractory period within the atrioventricular (AV) node, hydration status, and presence or absence of pharmacologic agents used to control the rate. When ventricular rate increases to tachycardic levels, a situation of atrial fibrillation with rapid ventricular response (AF with RVR) ensues. This in turn can lead to decompensation in the form of either myocardial ischemia or creation of congestive heart failure (CHF). The incidence of atrial fibrillation increases significantly with advancing age.
I add a link where you may find information on this subject that might be interesting

http://www.medicinenet.com
/atrial_fibrillation/article.htm


Hope this helps
Matador 89

Tachycarida is a heart rate above 100bpm. Atrial fibrillation is when the lower chambers of the heart go take over &go into an atrial rythem of exremely rapid heart beats & your heart basically quivers. AF, particularly when prolonged, can lead to strokes & sudden cardiac death.

Atrial fibrillation is when there is no organized electrical current through the atria. It basically quivers as the previous answerers have stated, BUT it is NOT a fast beat as some have implied.

Tachycardia is a fast heartbeat, (over 100 beats/minute) associated with the ventricles (main pumping chambers).

So how an electrical current usually flows through a heart is started with the SA node, which is the natural pacemaker of the heart. It then travels to the atria which causes them to contract and fill the ventricles with blood. The electrical current from there pauses a fraction of a second at the AV node allowing the ventricles to fill and then continues its pathway throught the ventricles causing them to contract.

When you have disorganized electrical current quivering the atrium the AV node isn't to sure what to do. Since the AV node "collects" the current as it leaves the atria and sends it on its way to the ventricles it "fires" when it "thinks" the atria have contracted fully. Sometimes with Afib the electical current from the atria sends many of these messages to the AV node and so it "fires" off many more times than normal causing the ventricles to contract at a much faster rate causing tachycardia.